Multifunctional catalyst based on sandwich-type polyoxotungstate and MIL-101 for liquid phase oxidations

A sandwich-type polyoxometalate {(TBA)7H3[Co4(H2O)2(PW9O34)2]} was immobilized for the first time into the three-dimensional porous metal-organic framework, MIL-101. The composite material Co4(PW9)2@MIL-101 was prepared and the incorporation of the Co4(PW9)2 was confirmed using a myriad of solid state methods (FT-IR, FT-Raman, powder XRD, SEM-EDX and ICP analysis). Co4(PW9)2@MIL-101 reveals to be an active, selective and recyclable catalyst for the oxidation of different substrates: geraniol, R-(+)-limonene, styrene and cyclooctane, using H2O2 as eco-sustainable oxidant. The stability and robustness of the heterogeneous catalyst was confirmed by different techniques. The MIL-101 framework demonstrates to be a suitable and efficient support to accommodate catalytically active sandwich-type polyoxotungstates.